drm/i915: Reduce locking inside swfinish ioctl
We only need to take the struct_mutex if the object is pinned to the
display engine and so requires checking for clflush. (The race with
userspace pinning the object to a framebuffer is irrelevant.)
v2: Use access once for compiler hints (or not as it is a bitfield)
v3: READ_ONCE, obj->pin_display is not a bitfield anymore
v4: Don't be creative with goto.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-14-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1d8858d..03e806c 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1518,26 +1518,23 @@
{
struct drm_i915_gem_sw_finish *args = data;
struct drm_i915_gem_object *obj;
- int ret = 0;
-
- ret = i915_mutex_lock_interruptible(dev);
- if (ret)
- return ret;
+ int err = 0;
obj = i915_gem_object_lookup(file, args->handle);
- if (!obj) {
- ret = -ENOENT;
- goto unlock;
- }
+ if (!obj)
+ return -ENOENT;
/* Pinned buffers may be scanout, so flush the cache */
- if (obj->pin_display)
- i915_gem_object_flush_cpu_write_domain(obj);
+ if (READ_ONCE(obj->pin_display)) {
+ err = i915_mutex_lock_interruptible(dev);
+ if (!err) {
+ i915_gem_object_flush_cpu_write_domain(obj);
+ mutex_unlock(&dev->struct_mutex);
+ }
+ }
- i915_gem_object_put(obj);
-unlock:
- mutex_unlock(&dev->struct_mutex);
- return ret;
+ i915_gem_object_put_unlocked(obj);
+ return err;
}
/**